Cathode-ray tube circuit



Dec.. 27, 1949 P. A. JEANNE cArHoDE- RAY TUBE IRcUIT 4` Sheets-Shes?l l Original Filed Feb. .24, 1944 /NVENTOR F. A. JEANNE Original Filed Feb'. 24, 1944 4 Sheets-Sheet 2 Dec. 27, 1949 P. A. JEANNE SAT1-IODE-RAY"TUBE CIRCUIT Original Filed Feb. 24, 1944 4 Sheets-Sheet 3 A 7' TOPNEY Dec. 27, 1949 P. A. JEANNE CATHODE-RAY TUBE CIRCUIT Original vFiled Feb. 24, 1944 VOL TAGE THIS SPAC/NG DEPENDENT C' oN RANGE uN/r sE rr/Nc 4 Sheets-Sheet 4 UMa/o REcE/VER our/ur [RANGE UN/ T OUTPUT PULSEl /OSC/LLOSCOPE PATTERN l s/aNAL man Hina d, A j |L TARGET s/aNALs-f-f 5 v 1 4 RANGE T/NE VNarcl-l /NVEN Tof? l? A. JEANNE ATTORNEY to a second set or' denection elements `in' Patented Dec. 27, 1949 2,492,700 CnfrHonE-i'tdiz TUBE' o'iitoin'r Baur: A31. Jeanne; Mount Ver-'non,--.r Y.; assigner to- Bell Telephone Laboratories, Incorporated,` New Yorkr- Ni Y.,. a corporei-,ioni of New- Yorkdriginei connection February' 24.- 1944; Seriel- No5.- 5233691 Divided and this application March 19;--1945'gisriaI-No. 583,5374 6 Claims. (CLBLS-Z 1i T-nisinvention@ relates toi auf indicating, system: and particularly' toi ani indicating system enr--v ployingi a,- cathode ray tube.' This application is a: division of application: Serial' No.l 5233691, nicely Fbrury 24', 1944, anni issued- February 25;. 1947, ti as Patent 2,416,;20.-

Theusefo'f acatnnde; rfytube as-an indicating- 2' duces squ'etrefpulses' ci; for example, 600 micro-M seconds duration once every 480th of a' secondi Whiclfi cutsf'oii tile-v sweepvalv to allow the .sweepA capacitor tol discharge: through a tube Whosev anodeec-athodepathis' connected across the sweep capacitor. This latter tube' in the normal siil'ecp` circuit would probably: be called a constant or viewing devicefiswell known inf-the' art.: Inca current" tube but inthe' present circuit theI cur typioalarrangerhent,thefcathoderay lleamgene`r-v rent fl'owi` therethrough maintained' substanated in-r the tube is deflected bymeans of' a vanylo tiallyfconstant' at one value1 during those portions ing: voltage, gane-g; the; Sweep voltage; applic-d of the sweepf cycle during which the time s'calej toene setlo'i-deilectinneminente-sothatitsweeps4 is". not enpanded'l-butf winch. has a puise applied; atiarknownirat@ van gppdeterminedpam; ont toi-its gridwcathodeicircuit to increase the rate of screen er: target to; providefaiinear" time? scale` or discharge' 0i? the corden'sertrueh this tube for axisTV and'tlie signals? g-...csui'al indiani-,inn of.: which; 15 the lenen-roi timeitisfdesiredrto expand the time is desired onetheiscreen tif-'said tube; aref applied scale; During-v the plfd 0fexpanson the current How isipreferably maintained substantially constant at; e; higher? value. The start of this manner es tclcause transverse deflections ci the.

pulse' canbeicontrolledlso"that any desired porbeamfrom its normalptii The dispositino the' latter. deflectonsaionql' a `normen path as'- dis'- pl'ayed onf the screen?. indicates' tlieftincf intervals. existing between tl'fe signal-ss andi trie width@ on each sgnal'- irnagefindicates itst time duratiorin along?? the scalef of a" slide' rule'. Moreover; the' irrord'erthct individuali signals orrrestrictedpcrdurf-ation or tlieple can' be varied to control the' tions off thetime scaif c'f the cathode ray indi- 25 dui-ietiriof cator tube may be closely observed, it is necessary in'y generalt'o expandfthe scale beyo'iidtle' available range o' the screenisl a result of? suoni sweepexpansion; mu'cl' riffA the totallsir'ee'pV range w'o-uldfbe` lost from' View; Tpre'vent this unde-- sirarfla result,-

Has'lcie'n heretofore proposed to` expand a portion onlyof the timing scale of* ani indcating circuit employing-ar cathode ray indicator'tube; Due tne increasedl speed' of' the sweep over tile -erpended portion of" tiley timing scale; the" brilliance` of tiret Visualt indication' orf the screen'within"tliisportionisnot as great as triatf'orthe rest crtnei'ndicationi in" the* swejep circuit s'oas toexpend the timing: It is an object" o f invention' toA provide' sc'tle' dtre oscilloscope foi" the duration of the' Ineens for intensifying tnefii'e'am of`a cathode ray; expansion notclo time" interval, for exdevice diningtriev time that tlr'e t'ini'n'g" scale i's Iample, may correspond to 1200 yards range. Tl'is neingexpa'nded: expansion noten orpulseA is also applied to en Itf-isanotlier object-'o tfiis-invention tdprovide nipiifyin'gci' uit td'produce an amplified negaw-catnode rey devic'einovelfs'weepi and' benin"l v sanieidurat'ion Wnicnisapplied intensityfvaryne* means: wttotlecetnode-'of-tne cathode ray' tube to' swing In" accordanceYWitlrt ai' spe'cilc embodiment of tlie potentiallf'oftlie cntnode negatively' with re# the invention" ctosenbyway of example-ferrant# s pect" oitliecontrolel'iilent therein and thereby poses of? illustration-i th'etbearnof a'catliodei rey I'"'c'1`"``aaseltile@niteiisty oftt'lie beam for the' period tube* inan intiic-z'atiilg devici`s intensfedfl ai; dove'idby-'the'eiipansinfnotcn or, in' other words;

controlisanalog'ons to' tli'at obtained by moving ains tniagniiyingfiiltleldirection of movement)- ode' ray`iifoie-ntinel device including the beam im tensify" ine'an'sI to be'- described below is employd-i radar'systnr; tl'ie-I indicating device" being utilizedtigive r'isiial presentation of one" 3W. moreecli'o pulses and, if desired, of direct 1on1-sesE from' tlrie' radar transmitter. A negative pulse' (called-'tile "expansion noten), the initiaton'- of Whichis controlled by a synchronizing pulse' from tli'ej radar pulse transmitter operating; til-rbiJigrlit a variable' delay' circuit or unit (called the 'rarigefu 'nit")"` ,V is utilized to produce a' i'ndsitivel` l`s`e Whi'cli controls the discharge tube' tnesametimelthaitne Waver om air-sfiiwaci'zfcircuity for the?period-'ci"5 tini'e'tififat trie time scale'- is einr pandd-- The) intention Will-'ibeniore readily understood by'f'refe'rringtoltlrlf following description taken in* connection with the-: accompanying drawings' form-ing? ab'p` arttherelb'v which:

isi expanded; Tlisswee1- crciiitfA way of cir-'i' ampie; compris-'es in sweep cpacitor wnicn is maintained inttneclffarged conditlonfby at sweep vai-vewnichzis nomi-olif conducting; and'Y ai iznil'srefA generator; celled:antistatic;sweextimer;weinen-pro#a 20- tionfcftnetimingiscalecan be' expanded. ThisY representations to aid in understanding the invention.

Referring more speciiically to the drawings,

Fig. 1 shows, by way of example for illustrative purposes, a radar system employing an indicating arrangement using a sweep circuit with ray intensity control in accordance with the invention. Fig. 1 is a single line block diagram to show the relationship of the various major elements of diagram. In the arrangement of Fig. 1, a high voltage rectifier I in the radar pulse transmitter 9 supplies about 12,000 volts direct current to a charging circuit or element I I. After the charging voltage builds up to ,about 21,000 volts, a rotary spark gap l2 discharges the capacitor in the charging circuit. This discharge takes place in about 1 microsecond and causes a magnetron oscillator in the radio transmitter I3 to oscile late for this brief period and send short pulses of radio frequency energy through a T-R box I4 to an antenna I5 which, for example, includes a wave guide and a parabolic reflector. A suitable antenna is disclosed in an application by A. P. King, Serial No. 499,450, iiled August 21, 1943. Radio frequency pulses from the antenna (called transmitted pulses or emitted pulses) strike one or more objects and produce reflections or echoes therefrom which are received by the antenna I5 and transmitted through the T-R box I4 to the receiver I 3. The Tp-R box may be of any desirable type, for example, a Western Electric Company '109A tube. This tube is essentially a resonant cavity filled with an ionizable gas. Dur-- ing reception of the low voltages of the received energy, the gas is not ionized, the cavity is tuned to resonance and the received energy is connected to the receiver I6. During the transmission of a pulse from the radio transmitter I3, the voltage due to the pulse ionizes the gas, thus detuning the cavity and preventing the energy of the pulse from reaching the receiver IS.

In the receiver I6 the received waves are heterodyned to a convenient intermediate frequency and these intermediate frequency waves are amplified, detected, amplied and applied to one of the vertical deiiecting-plates I1 of a cath-v ode ray oscilloscope I8. The received wavesv cause, for example, a sharp upward deflection of the trace of the cathode ray beam generated in the tube I8. A typical trace is shown in Fig. 7A, the pulse H0 representing the transmitted pulse and the pulses III being caused by reflections from targets.

Energy from the rotary spark gap I2 (which isy the initiation of each pulse in the rotary spark gap. A suitable range vunit is disclosed in anl application of L. A. Meacham, Serial No. 491,791,i filed June 22, 1943, and which issued June 17,-.

v1947, as Patent No. 2,422,204. The outputv pulse Energy from the rotary.

from the circuit 23 which is shown in Fig. 7--B is fed to an expansion notch generator 24 which produces a negative pulse II5 which has a duration corresponding, for example, to a range of 1200 yards. This pulse is shown in Fig. 7-E. A suitable circuit for producing such a pulse is disclosed in an application of B. M. Oliver, Serial N0. 486,780, filed May 13, 1943, and which issued .r-'as Patent No. 2,433,863 on January 6, 1948. This pulse is applied to the sweep circuit I9 to make a 'controllable portion of the sweep voltage wave .1 produced by this sweep circuit of a greater volte ge gradient than the rest of the wave and thus "to expand in the direction of the sweep the pattern on the oscilloscope screen for a distance cor- 'responding to the length of this pulse. A portion the system and is not intended to be a circuit .of the energy from the sweep circuit I9 is also a, plied by means of a connection 25 to an unvblanking circuit 26 to release the beam, which has been previously blanked oi, for a period of about 600 microseconds after the initiation of each pulse from thevrotary spark gap I2.

-. YThe pulse from the variable delay circuit 23 is also connected through a delay circuit 2.1 which f, .delays the pulse. for a period corresponding to about 400 yards range by producing a pulse II3 which is delayed from the pulse II2 by a period corresponding to a range of 400 yards. A suitable delay 'circuit is disclosed in the above-identified Oliver Patent. The delay interval is shown in Fig. '7-C. The delayed pulse is applied to a pulse generator 28 (called the "400-yard notch generator) which is, for example, similar to the expansion notch generator 24 except for some differences incircuit constants. This circuit gencrates, as shown in Fig. 7D, a pulse I I4 of a duration corresponding approximatelyV to 400 yards range. The output of the generator 28 is connected to the other one of the 'deilecting plates I'I in such a way that the energy of the notch is added to the energy from the receiver I6 so that an echo pulse appearsin the notch in the image on the oscilloscope screen in the manl circuit of Fig. 2 comprises a sweep circuit, an unblanking circuit, andan intensifier circuit.

The sweep circuit properly consists essentially of a diode 44 which passes negative pulses only, a single pulse multivibrator [comprising the tubes VI and V2 and called the basic sweep timer for triggering the sweep from the 10 toBO-volt negrativepulses supplied from the rotary spark gap I2 in the transmitter, a sweep v-alve tulbe V3 :by means of which the sweep condenser 3| is chargedax discharging tube V4 through which the condenser 3I is discharged at lone substantially constant rate for the entire Idischarge portion of the sweep cycle except for the period dure' ing which it is desired to expand the time scale when it is discharged :at a faster, and preferably constant, rate, a sweep voltage divider 32 and 33 and an inverter tube V5. Individual power supplies can -be providedfor each of the tubes but for simplicity in the drawing the :anodes of many The complete representation is shown in arcaico@ ci the' tubesfhave been shown connected through respective anode resistors to' the positive terminal of a 45o-volt direct current source 34 the negative terminal of `Whichlis connected to' ground and the anodes' of others ofthe tubes' have been shown connected through respective anode resistors to the positive terminal' of a SOO-.volt direct :current source whose negative terminal' is grounded. Negative 1 0 to 30-iolt pulses' oif'about 1.2 microseconds duration are Supplied to' the terminals 40 and 4 l' of the sweep circuit. A conventional coupling con-denser 42and .a leak resistor 43 are provided in the input circuit' of the tube VI along *with the diode 44 :which isv connected in the grid lead of the tube V| soi that negative pulses only are passed. Eight' csfthese pulses which are substantially concurrent with the "transmitted pulses are shown in Fig. Blf-A. The tubes V| Aand V2y comprise a single pulse multivibrator which produces relatively` square negative pulses lat least 600 microseconds long', the duration of the longest sweep. As there vare, for example, 480 pulses per second from the spark gap |2, there are intervals of more than 2,000' microseconds between transmitted pulses and the inactive periods are over 1400 microseconds long. These square negative sweep timing pulses produced by the basic sweep timer (see Fig. 3 0) are applied to the grid of the tube V3.

Considering now the basic sweep timer in somewhat greater detail, the anode of the tube Vi is connected through a.' .coupling condenser 45 to the grid of the tube V2 while the anode of the tube V2 is connected thorugh a coupling condenser 45 to the grid of the tube Vi.- A. leak resistor 41 is connected between the grid ofthe tube V| and ground, and -a leak resistor 48 is similarly connected between the grid of the tube V2 :and ground. Platevoltage for the anode of the tube VI is supplied from the source 34 through the resistors 49 land 50, the common terminal of these two resistors being connected to ground through a condenser 5|. Anode voltage for the tube V2 is provided by the source 34 through resistor-s 52 and 5l). The ,cathode ef tube VI is connected to ground while the cathode of" tube V2 is connected to ground through resistor 53. The cathode of the tube V2 is connected to the positive terminal of the source 34 through resistors 54 and 5t. A diode 55 is connected between the grid of the tube V2' and ground for stabilization purposes.

The laction-of the multivibrator circuit for generating square negative pulses of the type shown in Fig. 3*-C for basic sweep timing will now be described: statically when no pulses are being re- 'ceived trom the transmitter, the tube VI is passin g current whi-le the tube V2 is biased to cutoi. Therefore, the voltage at the plate Iof V2 is the full voltage ofV the source 34 (approximately 45,0 Volts), while that of the plate of the tube V| is less by the drop through the resistors 49 and 50. Furthermore, condensers 45 and 46 which couple the plates and grids of the tubes V| and V2 are charged to the-voltages of their respective plates, condenser 45 being charged at a higher potential. The negative synchronizing pulses applied between the terminals 40 and 4| from the transmitter serve only to trip the circuit, that is start the action of the multivibrator. When one of these -pulses is applied to the grid of the tube Vl, it tends to. drive this tube to cut-off causing a decrease in current through resistor 49 and a resultant rise in voltage in the plate of the tube Vl. As this voltage rises, condenser charges to a higher potential causing the grid of the tube 6 V2 to become more positive and the tube' V2' `to begin to cond-uct. Thus thev current through the resistor` 52. causes a drop in voltage 'at the plate fof the tube V2 and t sends a negati-Ve impulse through the condenser 46 causing theV grid ofthe tube V| to become' more negative, further cutting ori this' tube. The above," action once started by an incoming negativeI synchronizing pulse (such as one o f the pulses |100: shown in Fig. 3A orv pulses having a fixed phase relationship with respect thereto), is very rapid and' continues until tube V| is cut oi and tube V2 is passing current. The' tubes will remain in this condition until the grid of tube Vl is suiciently recovered from the negative -pul-se through the con-denser 46 toV permit tube VI to become conducting again. This depends on' the time required for the condenser 46i to discharge through the resistor 41. The values of resistance and capacitance are so chosen that the tube' V will' remain -cut ofi for' approxirn'ately 600 microseconds. The tubes thenrestore very rapidly to'their initial condition. The output or` the basic sweep timer at the plate |of the tube V2 is sa square negative pulse due to the r-apid drop and rise of voltage at this plate. Eight of these pulses |02 are shown in Fig. 3-C. This is the pulse needed to cut yoil the sweep .valve tube V3. In the action just described, the condenser 45 has attained a charge above its initial static condition when the voltagel at the plate of the tu'be V| rose land it must be dischargedbefore initial conditions can again be realized. Also it is desirable' to discharge this capacitor' quickh7 which can not be done` through the gri-d leak 481. The diode is used to provide a -low impedance discharge path to ground for this condenser and the multivibrator circuit is thus restored very rapidly to its initial condition before another incoming negative pulse' is applied.

The circuit constants of the sweep circuit shown on the drawing are such that the maximum sweep time is about 600 microseconds corresponding to a range of about 100,000 yards. The sweep expansion resistor 56 in the cathode of the dis,- charge tube V4 permits adjustment of the maximum sweep from' approximately 44,000 yards to 100,000 yards.

In the absence of a sweep timing pulse |02 from the basic sweep timer, the sweep valve tube V3 is normally passing current to charge the sweep lcondenser 3| through a circuit which includes ground, the sweep, condenser 3| the cath ode-ano`de path of the tube V3, resistor 5l', and the direct current source 34. When one of the basic sweep timing pulses |02 is applied to the grid of the tube V3 through the coupling condenser 54A, the current charging the sweep condenser 3| is interrupted and the condenser dis'- charges through the discharge tube V4 at ai constant rate (in the absence of a pulse from the notch expansion generator 24). The rate of discharge is determined by the characteristics of the tube V4 and the value of the resistance 56 which is shunted by the condenser 58. The output of the generator 24` is applied to an amplifier 'and phase inverter (shown by the box 35), the output of which is applied through coupling condenser 59 to the grid of the tube V4, a leak resistor 6i] being connected between the grid oi become square wave positive pulses which are fed to the grid of the tube V4 and also to the grid of the tube V7 in the intensifier circuit which will be described below. The positive pulses to the grid of the tube V4 cause this tube to pass a greater current for the duration of the 1200 yard notch, or in other words for a short time on either side of the 400 yard pulse produced by the notch generator 28 and which is, as shown in Fig. 5, centered in the 1200 yard notch pulse H5. The faster discharge of the sweep condenser 3l increases the sweep speed and therefore expands the sweep during the occurrence of the '7.2 microsecond pulse H5. Fig. B-D shows direct sweep pulses ID3 produced across the sweep condenser 3| in the absence of notch expansion pulses H5 at the tube V4, while Fig. B--E shows sweep pulses lofi. produced under these conditions in the output of the amplifier inverter tube V5. Fig. 3-G shows the timing of the notch pulses and notch expansion pulses with respect to the transmitted signal pulses shownin Fig. 3-A while the same thing is shown, for a larger scale, in Figs. 7--D and 'T E. It will be noted that each notch pulse I I4 lags its corresponding transmitted pulse H0. This lag is also shown in Fig. 6, which is a combination of Figs. 4 and 5, and wherein pulse I I is the transmitted signal pulse after reception and detection and pulse I I I is the echo pulse bracketed by the 400 yard notch pulse H4. Fig. 4 shows the pulses I I0 and III alone while Fig. 5 shows the pulse I I4 with respect to the time position of the pulse I l0. The 400 yard notch pulse H4, as pointed out above and as shown in Fig. 7, is started 400 yards after the pulse H2 produced by the range unit 23. The expansion notch generator 24 produces a pulse H5 which starts with the pulse produced by the range unit 23 and extends over a period corresponding to a range of 1200 yards, or, in other words, it starts 400 yards before the time of the pulse H4 produced by the notch generator 28 and extends for a time interval corresponding to a 400 yard range after the notch pulse H4 has been completed. Thus the sweep wave is said to be expanded during the occurrence of the pulse from the expansion notch generator 24. This period of notch expansion is shown by the portion I01 in the pulses |06 in Fig. 3-H. Referring again to Fig. 6 it is noted that the direct pulse I I0 appears narrower than the echo pulse III. This is because there is no expansion during the reception of the direct signal, hence it appears narrower than the echo.

The wave shown in Fig. 3--H is applied through condenser 5I to one of the deiiecting plates' 22 in the cathode ray tube I8. A voltage 180 de grees removed from the Voltage wave shown in Fig. B-H is applied to the other of the deflecting plates 22 by means of the condenser 62 which is connected to the plate of the amplifier-inverter tube V5. The grid 0f the tube V5 is connected by means of the resistor 63 to the common terminal of the condensers 32 and 33. To drive the inverter V5, about a tenth of the total sweep voltage from the condenser 3l is taken from the voltage divider formed by the condensers 33 and 32. The amplification in the tube V5 produces an output approximately equal to the direct sweep voltage applied to one of the plates 22 by means of the condenser 6 I. Bias for the tube V5 is provided by means of a resistor 64 while the grid leak resistor 65 is connected in the circuit between the grid of the tube V5 and ground. The diode 66 is connected across the condenser 32 in lil in its output. The eiiect of the diode 66 under,

dynamic conditions is therefore t0 stabilize the initial potential impressed on the input of the inverter V5 at the beginning of each sweep, this initial potential being limited to approximately that of ground. Without the diode 66, variations in the time interval between successive signals from the xed average would cause some iiuctuations in the horizontal deiiecting force, thereby some fuzziness ofl the image since images of successive signals would not exactly coincide on the screen. The function of the inverter V5 is to reverse the phase of the voltage I 03 and produce inverted sweep pulses |04 so that the eiiects of the two horizontal deflecting plates 22 on the beam are additive, that is, when one plate attracts the beam, the other repels it.

The longest sweep impulse lasts about 600 microseconds so that at the rate of 480 per second, the inactive intervals between sweep impulses are 1400 microseconds or more. If the electron beam struck the screen continuously a bright spot` would be produced at the start of the sweep and the return of the beam would be visible across the screen. To eliminate these undesirable features, the beam in the cathode ray tube I8 is nerf mally blanl'red oit by iixing thestatic or continuous biasing voltage of the grid 31 therein at a sufficiently negative value to cut the beam oi and positive pulses sufficient to release" the beam are applied to the grid only during the interval when sweep impulses are applied to the horizontal deecting plates 22. The biasing voltage is applied to the grid 3l from tap 14 of the potentiometer 'l0 connected across a. suitable con# stant source of power (not shown). The cathode 30 is connected to a tap 'II thereon through a resistance 'I2 and one of the focussing anodes 38 is connected by means of the tap 'I3 to a point on the potentiometer 'lil which is positive with respect to the potential of the cathode 30. The control element 3l of the cathode ray tube is con-p` nected to the tap 'I4 on the potentiometer 'I0 (which is negative with respect to potential of the cathode 3G) through the resistor 15. The second anode 39 of the cathoderay tube is connected to a tap 'i6 on potentiometer I'I which is connected to a second power supply (not shown).` This is done to provide means for placing the second anode at the average potential of the plates Il which are directly connected to the receiver output tube. The tap 'I6 is at a positive potential with respect to thel potential ofthe tap 'I3 on the potentiometer 10. The values of the' potentials applied to the members 30, 31, 38 and 39 are chosen, in accordance with well-known practice, so as to produce a ne spot on the screen The circuit arrangement for generating the un blanking pulses comprises the tube V6 and associated circuit connections. The square negative pulses from the output of the basic sweep timerj VI-V2 are applied through coupling condenser- 80 to the control :grid ofthe tub/e The grid leak resistor 8l is provided between the control grid 'and ground, the cathdebeing connected directly to grbund. The anode o-the tube V6 is cnnectedthrough resistor `02 to' "the positive terminal vof the source-35 land `through coupling condenser 8-3 to the `control 'element :31 of the cathode ray tube I0. Y

The sharply-peaked negative voltage across the resistor 8|V in series with the lcoupling condenser 8 0 is applied to the control 'grid of the tube V5, driving this tube to cut-01T by the time each negative pulse |02 shown in 3- C has reached but a-smal-l fraction of its ultimate value. AThuis the output voltage Vat the plate of the V6 rises sharply due to the decreased voltage v4drop through its plate resistor 82. The voltage of the plate remains at this increased positive value until tube V6 again becomes conducting when the input pulse repasses the cut-off voltage. This rise and fall of the voltage of the plate of the tube V5 sends a positive pulse through the coupling capacitor 83 to the control element 31 releasing the cathode ray tube beam. These unblanking pulses are shown as the pulses |05 in Fig. 3-F. The time that the grid of the tube V6 is held below the cut-off voltage determines the duration of the unblanking pulse. As mentioned above, this time is about 600 microseconds.

Due to the fact that the beam is swept at a faster rate across the screen during the time of expansion, the image on the screen during that period of time is not as bright as for the rest of the image. To compensate for this an intensier circuit comprising the tube V1 and its associated circuit connections has been provided. Positive pulses corresponding in time duration to the 1200 yard negative pulse H5 produced by the expansion notch generator 24 are applied tothe grid of the tube V1 through the coupling condenser 00 and resistor 9|. A grid leak resistor 92 is connected between the common terminal of the members and 9! and ground and the cathode of the tube V1 is connected to ground through the biasing resistor 93. The anode is connected through the anode resistor 94 to the positive terminal of the source 35. The action of the tube V1 is to amplify each positive pulse applied to its grid to produce a negative pulse which is applied to the cathode 30 of the cathode ray tube I8 through coupling condenser 95. This causes the cathode of the tube i8 to swing in a negative direction to intensify the beam during the period of time spanned by the pulse produced by the expansion notch generator 24. This period is represented between the points A and B in Fig. and in Fig. '7--F.

It will be apparent that by making use of the circuit arrangement described above, the linear time scale is expanded between the points A and B of Fig. 5 and of Fig. '1-F and the positions of these points with respect to the transmitted pulse l l0 can be varied by varying the time of generation of the pulse in the range unit 23. Thus if 'the range unit pulse H2 is generated after a shorter time interval following the corresponding Ypulse l l0, the period of expanded sweep shown in Fig. 5 and Fig. '1-F moves to the left as does also the 400 yard notch pulse H4 which is always centered within the period of the expanded sweep. The pulse l IQ is centered with respect to the selected echo l l l either by manual means or by any suitable automatic means.

Circuit constants of an arrangement in accordance with the invention which has been actually constructed and satisfactorily operated have been indicated on the drawings. It is sto be understood, however, that the invention is not limited to the use -of elements having these particular 4circuit constantsgas it is obvious that changing the frequency of pulsing, the length of the pulse produced by the expansion notch generator Yor varying the length of the `sweeptirning pulses are examplesof various lchanges which might lbe made and which will cause changes in the circuit constants. l

Although the present invention has been described in terms or the preferred illustrative embodiment, it will be realized that the invention and its several features are susceptible of embodiment in a wide variety of other forms and hence tnc invention is tote" Yunderstcori .as "comprehending such other forms as may fairly come within the spirit and letter of the claims.

What is claimed is:

1. In combination, a cathode ray tube comprising means for generating a beam of electrons, a screen or target for said electrons, and means for deflecting said beam, means for applying a cyclically recurring defiecting wave to said deflecting means for sweeping said beam across said screen, each cycle of said wave having a sweeping portion and a flyback portion, said wave having its rate of change of amplitude in one part of the sweeping portion thereof higher than in any other part of said sweeping portion, and means for intensifying said beam during the period when said rate is higher.

2. The combination of elements as in claim 1 in which said last-mentioned means comprises means for applying a voltage pulse which has a duration equal to that period of time during which said deiiecting wave has its higher rate of variation to said beam generating means to increase the intensity of said beam.

3. The combination of elements as in claim l in which the sweeping portion of each cycle of said deecting wave has a changing amplitude in a relatively short portion thereof which is followed by a relatively long portion in which there is substantially no amplitude change.

4. In combination, a cathode ray tube comprising means for generating a beam of electrons, a screen or target for said electrons, and means for deecting said beam, means for applying a cyclically recurring deecting wave to said deflecting means for sweeping said beam across said screen, each cycle of said wave having a sweeping portion and a lyback portion, said wave having its rate of change of amplitude in one part of the sweeping portion thereof higher than in any other part of said sweeping portion, and means for varying the intensity of said beam during the period when said rate is higher.

5. A control circuit for a cathode ray tube having beam deflecting electrodes and a beam intensity control element, comprising means for applying a varying sweep voltage of predetermined direction to said electrodes, means for changing the rate of variation but not the direction of said sweep voltage for a predetermined interval, and means actuated by said last-named means for applying a control signal to said control element to alter the brightness of the beam trace during said interval.

6. A control circuit for a cathode ray tube having beam deiiecting electrodes and two beam intensity control elements, comprising means for applying a varying sweep voltage of predetermined direction to said defiecting electrodes, means 11 for applying a voltage between said control elements to normally blank said beam, means for applying a pulse to one of said control elements to unblank said beam for substantially the duration of the sweeping portion of each cycle of sweep voltage, means for changing the rate of Variation but not the direction of said sweep voltage for a predetermined interval, and means actuated by said last-mentioned means for applying a control signal to the other of said two control elements to alter the brightness of the beam trace during said interval.

PAUL A. JEANNE.

REFERENCES CITED The following references are of record in the file of this patent:

Number 12 UNITED STATES PATENTS Name Date Bagno et al. Aug. 4, 1942 Read, Jr. Mar. 16, 1943 Christaldi Aug. 8, 1944 Shrader et al Nov. 28, 1944 Cook Jan. 30, 1945 Cook Jan. 30, 1945 Thompson May 8, 1945 Theisen Oct. 9, 1945 Miller May 7, 1946 Theisen May 7, 1946 Moe Jan. 14, 1947 Bliss Oct. 14, 1947 Isbister et al Nov. 16, 1948 

